1. Field of the Invention
This invention relates to elastomeric poly(aryloxyphosphazene) polymers, to flexible and rigid foams produced from said polymers and to a process for preparing the polymers, foams and foam coatings. The polymers of this invention are soluble in tetrahydrofuran, benzene, and dimethylformamide, and exhibit excellent flame retardant and foam-forming properties. Foams prepared from the polymers exhibit excellent flame retardant properties and produce low smoke levels when heated in an open flame. Foams prepared from such materials provide protective coatings which are stable to heating.
2. Description of the Prior Art
The preparation of poly(aryloxyphosphazene) polymers has been disclosed in U.S. Pat. No. 3,856,712, Reynard et al; U.S. Pat. No. 3,856,713, Rose et al; and U.S. Pat. No. 3,883,451, Reynard et al. However, in contrast to the polymers of the present invention, the polymers described in the first-mentioned Reynard et al patent are copolymers that contain selected quantities of both aryloxy and alkoxy side chains in the copolymer backbone, whereas the polymers described in the latter-mentioned Reynard et al patent are copolymers characterized by the presence of halogen-substituted aryl side chains in the copolymer backbone. The copolymers disclosed in the above-mentioned Rose et al patent further differ from the polymers of the present invention since they are characterized by the presence of only alkyl-substituted aryloxy and unsubstituted aryloxy side chains.
Curable phosphazene polymers are disclosed in U.S. Pat. No. 3,888,799, Rose et al, and U.S. Pat. No. 3,702,833, Rose et al, where the cure sites are unsaturated groups capable of crosslinking. However, these two patents disclose copolymers having a high percentage of fluorine and are significantly different than the polymers disclosed herein. U.S. Pat. No. 3,948,820, Reynard et al, discloses curable phosphazene polymers in which the curing takes place by reaction of functional groups appended to the phosphorus-nitrogen backbone. U.S. Pat. No. 3,994,838, Thompson et al, discloses polyphosphazene foam vulcanizates in which vulcanization results from crosslinking of an added unsaturated material, the polyphosphazene acting as a non-reactive additive.
Other related art may be found in U.S. Pat. Nos. 3,515,688; 3,700,629; 3,702,833; and 3,856,712; but in each case, the polymers described in these patents differ from the polymers of the present invention in their structure and physical characteristics.